Recently I’ve been using Spar finish. On the second use from can #1 I noticed some clumps. I returned the can thinking it was a dud.

The same thing happened with can #2. After using most of the can (leaving a considerable amount of air space in the can), I checked the can after about one week of sit time. Sure enough the remaining finish had a dried membrane on top.

Yes I sealed the can lid with a mallet each time.

Is spar finsih susceptible to this? How do you fight against it?

-- Eric

21 replies so far

Usually finishes say to store them in a cool dry place. the other thing I do is buy my material in quart containers even though they cost more than gallons but last longer. There’s also a product that you spray in the can just before closing the can that replaces the air that helps preserve the finish.

I have the same problem with Spar Urethane. I have even poured it into glass jars, filling them to eliminate air space and a few weeks later it has turned to gel/goo. The Bloxygen Jim cited works pretty well but is pricey and I hate paying for something that feels like an empty spray can!

I place the UNLIT tip of a Propane Torch into the container and open the valve for several seconds … Propane is heavier than air, so it will displace it. Much cheaper than commercial blockers, and it seems to work. OTOH … exhaling into the can is even more economical, so if it works … why not ???

I’ve also heard of placing discs of Saran Wrap or waxed paper on the surface, but have you to try it … sounds like it should work … ANYTHING to keep Oxygen from contact with the finish.

BE SURE to never return finish to the container that has been out in the open … it will cause the exact same effect.

-- - dabbling in sarcasm is foolish … if you’re not proficient at it, you end up looking stupid … ... ...

I too use my propane torch to preserve the spar varnish sorry I forgot to tell you to do this eric My buts the product jim recommends is inert and not flammable therefore it is the preferred method to preserve the stuff. I hardly ever have a can for more than a few days. I always buy the smaller containers to be sure they stay fresh I have never tried exhaling but if that works I would stick with that it is cheep. you know these guys should tell you to buy beloxigen when they sell you a gallon of spar varnish.

Anyone ever try mixing vinegar and soda in a pitcher then pouring the gas (not the liquid) into the container and placing the lid on it? I saw where a guy got money for this suggestion but have never tried it myself. Just wondering.